The present invention relates to a liquid distribution device for a multitubular falling film heat exchanger and to an exchanger fitted with such a device.
A multitubular heat exchanger generally consists of a bundle of parallel tubes within an outer shell. Two liquid flow systems have to be considered; the first is outside of the tubes and the second is inside the tubes. An entry channel usually receives the fluid being distributed to the insides of the tubes and an exit channel receives and discharges the fluid that has passed through the tubes. Separation between the two fluid systems is ensured by providing two spaced apart, tube plates, that extend across the shell and into which the ends of the tubes of the bundle are welded.
It has been found, that if the fluid flowing into the inside of the tubes is a mixture of a non-dispersed liquid phase and a gas phase, for instance a liquid phase in the presence of its saturated vapor, one frequently encounters an inequality of distribution of the liquid phase between the tubes of the bundle.
Various means have been developed in the past for improving the distribution of a homogeneous liquid phase between the tubes of a multitibular exchanger. One such means is described in "Die Bemessung der Zu-und Abflusshauben von Warmeaustauschern" (Dimensioning of the entry and exit bonnets of heat exchangers), Kaltetchnik, 15th year, volume 3 (1963), page 85. This article describes the use of concentric partitions arranged in the entry channel of the exchanger or of a disc with holes in it arranged in the entry channel perpendicular to the axis of the exchanger. It should be noted that such a disc does not occupy the whole available cross section of the entry channel.
Further French Pat. No. 2,268,178 describes the placing of a perforated filleted cap in the entry channel of an exchanger. This filleted cap is open at its top and is situated at the entry of the entry channel of the exchanger.
These prior art devices, however, are not satisfactory if there is a liquid phase and a gaseous phase. In this case the liquid, which enters in the upper part of the entry channel of the exchanger, always moves preferentially toward the central tubes of the bundle of tubes, although to a lesser extent when compared with exchangers not fitted with these devices at all.